This application claims benefit of Japanese Application No. 2000-151462 filed in Japan On May 23, 2000, the contents of which are incorporated by this reference.
The present invention relates generally to a portable image display, and more particularly to a portable image display that can be added to portable telephones or portable information terminals.
In recent years, image displays, especially head or face mounted image displays designed to allow individuals to enjoy images on large screens or for other purposes have been under intensive developments. With the recent spread of portable telephones or information terminals, there is also a growing demand for viewing images or textual information on portable telephones or information terminals on large screens.
Among head mounted image displays known so far in the art, there is a display system comprising a CRT or other image display device, an image transmission device for transmitting an image on the image display device to an object plane and a toric reflecting surface for projecting the image on the object plane in the air (see U.S. Pat. No. 4,026,641). There is also available a refraction type image display system comprising a relay optical device for forming an image on a liquid crystal display (LCD) or other image display device in the air, and an eyepiece optical device including a decentered concave mirror for guiding the thus formed image to the eyeball of an observer (see JP-A 06-294943).
However, these systems, because of using a large optical system, are found to be unsuitable for use on portable telephones or information terminals.
In view of such problems with prior art as mentioned above, an object of the present invention is to make an observation portion of an image display system so compact that it can be mounted on a portable telephone or information terminal.
According to one aspect of the present invention, this object is achieved by the provision of a portable image display having data communication means, which comprises a speaker portion for catching sounds, a microphone portion for picking up sounds, an image display device and a viewing optical system for forming an exit pupil to view an image displayed on the image display device and having a generally positive refracting power, characterized in that:
said viewing optical system is constructed of at least one prism member comprising an entrance surface through which a light beam emanating from said image display device is entered into a prism, at least one reflecting surface at which said light beam is reflected within the prism and an exit surface through which said light beam leaves the prism, wherein said at least one reflecting surface has a curved surface shape for imparting power to a light beam, said curved surface shape being defined by a rotationally asymmetric surface shape capable of making correction for decentration aberrations.
Reference is now made to the action of this arrangement. Especially for a portable image display increasingly required to have smaller size, it is preferable that the optical system for forming an exit pupil and having a positive refracting power is constructed of one prism member having a lens action. By use of one prism member, it is possible to achieve an optical system of smaller size. To obtain satisfactory aberration performance, it is preferable that the prism member comprises an entrance surface through which a light beam emanating from an image display device is entered into a prism, at least one reflecting surface at which the light beam is reflected within the prism and an exit surface through which the light beam leaves the prism, wherein said at least one reflecting surface has a curved surface shape for imparting power to a light beam, said curved surface shape being defined by a rotationally asymmetric surface shape capable of making correction for decentration aberrations.
According to the second aspect of the present invention, there is provided a portable image display having data communication means, which comprises an image display device and a viewing optical system for forming an exit pupil to view an image displayed on the image display device and having a generally positive refracting power, characterized in that:
said viewing optical system comprises a prism portion and a reflecting portion having a reflecting surface,
said image display device and said prism portion are received in a body of said portable image display,
said reflecting portion is held by a separate frame member, and
said frame member is receivable in said body.
Reference is now made to the action of this arrangement. To achieve an optical system of smaller size for a portable image display, it is effective to make use of a reflecting portion held by a frame member receivable in the body thereof. As mentioned above, size reductions may be accomplished by use of one prism member. If the reflecting member having a reflecting surface is designed to be receivable in the body, then the size of the portable image display can be much more reduced.
According to the third aspect of the present invention, there is provided a portable image display having data communication means, which comprises a speaker portion for catching sounds, a microphone portion for picking up sounds, an image display device, a viewing optical system for forming an exit pupil to view an image displayed on the image display device and having a generally positive refracting power, an image pickup device and an image pickup optical system for forming an image on the image pickup device, characterized in that:
said viewing optical system is constructed of at least one prism member.
Reference is now made to the action of this arrangement. The portable image display of the present invention may further comprise an image pickup device and an image pickup optical system for forming an image on the image pickup device. To reduce the entire size of the image display, it is preferable that the viewing optical system is constructed of at least one prism member.
According to the fourth aspect of the present invention, there is provided a portable image display having data communication means, characterized by comprising a first image display device having a pixel pitch Pm, a second image display device having a pixel pitch Pn and a viewing optical system for forming an exit pupil to view an image displayed on the first image display device and having a generally positive refracting power, and satisfying the following condition (1):
0.01 less than Pm/Pn less than 0.8xe2x80x83xe2x80x83(1)
The action of this arrangement is now explained. With a portable image display, textual or imagewise data on a display device are directly viewed or viewed on an enlarged scale. Especially when images of high definition are viewed through a viewing optical system having a generally positive refracting power on an enlarged scale, it is preferable to make use of an image display device having a fine pixel pitch. For direct viewing of images not through any magnifying optical system, on the other hand, no problem arises even when the pixel pitch is more or less large. Usually, an image display device having a fine pixel pitch is unfavorable in terms of cost. Accordingly, it is preferable to make use of an image display device having a large pixel pitch for direct-view purposes. For these reasons, the present invention uses a direct-view display device and a magnifying display device which satisfy condition (1).
To improve the easy-to-carry capability of the portable image display, it is required to make the magnifying optical system compact. For direct viewing with ease of use, on the other hand, this optical system must have a large display area. To this end the following condition (2) should preferably be satisfied.
0.01 less than Sm/Sn less than 0.5xe2x80x83xe2x80x83(2)
Here Sm is the display area of the magnifying image display device and Sn is the display area of the direct-view image display device.
To allow the portable image display of the present invention to achieve high-definition views of a magnified image with size and cost reductions, it is preferable to satisfy both conditions (1) and (2).
According to the fifth aspect of the present invention, there is provided a portable image display having data communication means, characterized by comprising a data storage means, a means for indicating the end of data reception, an image display device and a viewing optical system for forming an exit pupil to view an image displayed on the image display device and having a generally positive refracting power.
Reference is now made to the action of this arrangement. When an image is viewed through the viewing optical system, the user does not often peer through the viewing optical system during reception of the data to be viewed. Especially when the data are viewed on an enlarged scale, a long-duration view offers user fatigue. For this reason, it is preferable to provide the means for indicating the end of data reception. For instance, the end of data reception may be indicated by allowing a light to come on or a sound.
In the present invention, it is preferable to satisfy condition (1). More preferably, however, the following condition (1-2) should be satisfied.
0.03 less than Pm/Pn less than 0.5xe2x80x83xe2x80x83(1-2)
In the present invention, it is preferable to satisfy condition (2). More preferably, however, the following condition (2-2) should be satisfied.
0.04 less than Sm/Sn less than 0.3xe2x80x83xe2x80x83(2-2)
For correction of aberrations, the prism member used for the viewing optical system should preferably comprise at least two surfaces for reflecting a light beam within a prism. Preferably in this case, said at least two surfaces are each defined by a rotationally asymmetric surface shape.
In each of the arrangements according to the present invention, it is preferable to use a data storage means for magnified viewing.
For instance, images transmitted using a communication function are displayed on the image display device, so that they are viewed on an enlarged scale through the viewing optical system. To retrieve the required data or transmit them to separate equipment, it is preferable to provide storage means for storing the desired data.
In each of the arrangements of the present invention, there should preferably be provided a light source for illuminating the image display device and an illumination optical system for illuminating the image display device.
In each of the arrangements of the present invention, it is preferable for energy savings that when a plurality of image display devices are used, the image display devices not in service are not illuminated.
In each of the arrangements of the present invention, it is preferable that when an image on the image display device is viewed, the image is turned on the basis of whether the body of the portable image display is held by the right hand or the left hand.
In each of the arrangements of the present invention, it is preferable that the microphone portion for picking up sounds extends from the body of the portable image display such as a portable telephone.
In each of the arrangements of the present invention, it is preferable that the speaker portion for catching sounds extends from the body of the portable image display such as a portable telephone.
In each of the arrangements of the present invention, it is preferable that the speaker portion, operating portion and magnifying viewing optical system are mounted in order from the top side of the body.
In each of the arrangements of the present invention, it is preferable that a liquid crystal display (LCD) or plasma display may be used for the image display device.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.